RF antenna producing a uniform near-field Poynting vector

1. An apparatus for generating plasma, comprising: a quadrupole antenna configured to be disposed over a dielectric window of a plasma chamber, the quadrupole antenna including a first coil defining a first spiral dipole antenna (SDA) and a second coil defining a second SDA, wherein at least two adjacent coil segments propagate current in opposite directions relative to each other.

2. The apparatus of claim 1 , wherein the first coil is in a nested arrangement within the second coil on a plane.

3. The apparatus of claim 2 , wherein the nested arrangement places a turn of the first coil of the first SDA to be adjacent to a corresponding turn of the second coil of the second SDA as the first and second coils spiral from a center region to an outer region of the quadrupole antenna.

4. The apparatus of claim 1 , wherein the first SDA and the second SDA are vertically separated by a distance, such that the first SDA is in a first plane and the second SDA is in a second plane that is parallel to the first plane.

5. The apparatus of claim 4 , wherein the first SDA and the second SDA each spiral from a center region of the quadrupole antenna in a same clockwise or counter-clockwise direction.

6. The apparatus of claim 1 , wherein the first SDA is continuous from end-to-end and includes a first center point connected to ground, wherein the second SDA is continuous from end-to-end and includes a second center point connected to ground, and wherein the first center point of the first SDA is oriented 180 degrees from the second center point of the second SDA.

7. The apparatus of claim 6 , further comprising: wherein the first SDA is configured to receive a first radio frequency (RF) signal at a frequency from a first RF power source at a first near distance to the first center point via a first slidable connection, the first near distance tunable for impedance matching between the first RF power source and the first SDA, wherein the second SDA is configured to receive a second RF signal at the frequency from a second RF power source at a second near distance to the second center point via a second slidable connection, the second near distance tunable for impedance matching between the second RF power source and the second SDA.

8. The apparatus of claim 7 , wherein each of the first SDA and the second SDA has a length approximately equal to half the wavelength corresponding to the frequency of the first RF signal and the second RF signal.

9. The apparatus of claim 7 , wherein the first RF signal and the second RF signal are out-of-phase, and wherein the quadrupole antenna is configured as a counter current array, such that the first RF signal resonates a first RF current in the first SDA, and the second RF signal resonates a second RF current in the second SDA that is counter to the first RF current.

10. The apparatus of claim 9 , wherein the first RF signal and the second RF signal are 180 degrees out-of-phase.

11. The apparatus of claim 7 , wherein the first RF signal and the second RF signal have equal powers.

12. The apparatus of claim 1 , wherein the quadrupole antenna is disposed over the dielectric window by a separation that is tunable for impedance matching.

13. The apparatus of claim 1 , further comprising: an actuator coupled to the quadrupole antenna and configured to adjust a separation between the quadrupole antenna and the dielectric window to perform impedance matching between a first RF power source and the first SDA and a second RF power source and the second SDA.

14. The apparatus of claim 1 , wherein corresponding ends of the first SDA and the second SDA in combination radiate a displacement current, wherein the quadrupole antenna produces an electromagnetic field passing through the dielectric window as a surface wave along a plasma-window interface, the surface wave exciting and ionizing at least one process gas to generate plasma within the plasma chamber.